The International Medical Prevention Registry on Venous Thromboembolism (IMPROVE) is a prospective cohort study of physician practices in the provision of prophylaxis against venous thromboembolism (VTE) in hospitalized medical patients. Key endpoints include type and duration of prophylaxis, as well as death, clinically apparent VTE, and bleeding within 3 months following hospital discharge. This registry currently includes hospitals in 11 countries. IMPROVE online Data Submissions are secured using Secure Sockets Layer (SSL) technology.